Knock-out bar for presses

ABSTRACT

A KNOCK-OUT MECHANISM FOR A PRESS COMPRISING A KNOCKOUT BAR EXTENDING THROUGH THE SLIDE WITH KNOCK-OUT PIN ADJUSTABLY SECURED TO THE ENDS OF THE BAR. THE PINS ARE ADAPTED TO ENGAGE A SURFACE ON THE PRESS FRAME. PRESSURE PINS COOPERATIVE WITH THE BAR TO EJECT THE WORKPIECE.

. my Mxw Feb. 9, 1971 INVENTOR. WILLIAM F HOLLENBECK FIG 2 I x. I

1. ATTORNEYS.

United States Patent 0 3,561,245 KNOCK-OUT BAR FOR PRESSES William Frank Hollenbeck, Hastings, Mich., assignor, by

mesne assignments, to Gulf Western Industrial Products Company, Grand Rapids, Mich., a corporation of Delaware Filed Sept. 6, 1968, Ser. No. 757,936 Int. Cl. B21d 45/00 US. Cl. 72-345 2 Claims ABSTRACT OF THE DISCLOSURE A knock-out mechanism for a press comprising a knockout bar extending through the slide with knock-out pins adjustably secured to the ends of the bar. The pins are adapted to engage a surface on the press frame. Pressure pins cooperate with the bar to eject the workpiece.

This invention relates to the art of presses and, more particularly, to a knock-out bar mechanism for ejecting a workpiece from the die of a press.

The knock-out type of mechanism generally refers to the mechanism for ejecting a workpiece from an inverted die attached to the slide of a press and may be distinguished from a lift-out mechanism which acts from under the bolster of a press to lift the workpiece from the die on the bolster. Slide associated knock-outs are of three general types: cross bar knock-outs, cam knock-outs and knock-outs actuated by springs or air cushions. This invention is concerned with the cross bar type of knockouts.

The cross bar knock-outs of the prior art normally employ a bar which extends through a slot in the Slide and which contacts some form of adjustable stop on the press frame to stop the movement of the knock-out bar at a predetermined point in the press cycle. Pressure pins cooperating with the knock-out bar cause the workpiece to be ejected.

This prior art arrangement typically required some form of bracket or adjusting mechanism or a combination of a bracket and adjusting mechanism bolted or fastened to the frame of a press and against which the knock-out bar engaged. The bracket or adjusting mechanism could be adjusted on the frame so that the knock-out bar engaged the stop at the proper point in the up stroke of the slide; however, such adjusting mechanism or brackets required machining of the press frame as well as manufacturing of the specific adjusting stop device which was to be employed. Moreover, once the knock-out bar engaged the relatively rigid stop on the frame, there was no safety mechanism to eliminate possible damage to the press or the die if the proper adjustment had not been made.

It is an object of this invention to provide an improved cross bar knock-out mechanism for a power press.

Another object of this invention is to provide a knockout bar mechanism which requires no brackets or adjusting mechanisms on the frame of the press.

Still a further object of this invention is the provision of a knock-out bar assembly which is of simple and economical construction.

A further object of this invention is to provide an improved knock-out bar mechanism which minimizes possible press or die damage in the event an improper adjustment has been made or if an overload condition should occur.

More specifically, this invention contemplates a knockout bar which operates in a slot in the press slide. The knock-out bar may be retained in the slot by roll pins or other suitable means. Adjustable slip type knock-out 3,561,245 Patented Feb. 9, 1971 pins are carried at either end of the knock-out bar with the pins being adjustably clamped in the knock-out bar. The knock-out pins are adapted to engage an abutment surface on the press frame. Die pressure pins extend from the die through the slide to the knock-out bar and are adapted to eject the workpiece from the die when the knock-out bar and knock-out pins have engaged the press frame. Thus, during the down stroke or work cycle of the press, the die pressure pins force the knock-out bar up or away from the face of the slide; during the up stroke or retract cycle of the press, the knock-out bar is carried upward by the slide until the knock-out pins contact the press frame thereby halting the travel of the knock-out bar. As the slide continues to move up or retract, the pressure pins act to eject the workpiece from the die. The point in the cycle at which the knock-out pins engage the frame may be varied simply by adjusting the clamping relationship between the pins and the bar.

Other objects and features of the invention will become more apparent upon a complete reading of the following description which, together with the attached drawings, discloses but a preferred embodiment of the invention.

Referring now to the drawings wherein like reference numerals indicate like parts in the various views:

FIG. 1 is a fragmentary sectional view through a press slide showing the die in closed position and the pressure pin retracted.

FIG. 2 is a fragmentary sectional view similar to FIG. 1 showing the slide in retracted position with the pressure pins extended to eject the workpiece from the die.

FIG. 3 is an end elevation view of the knock-out bar and knock-out pin assembly.

Referring now to FIG. 1, there is illustrated one arrangement of a press slide and die in which the knockout bar of this invention has utility. It is to be understood that the specific arrangement illustrated herein is but one example of how the invention may be employed and is not intended to be limiting.

In FIG. 1, a reciprocating slide 10, which may be driven in any conventional manner, is adapted for reciprocation in a press having a frame 12. Secured to the slide is a punch holder 14 on which there is carried a punch 16. The punch is adapted to cooperate with a draw ring 18 and a die plug 20 supported on a die holder 22. Pressure pins 24 project through the die holder 22 in a conventional manner to cooperate with the draw ring 18. A knock-out plate 26 is received within the punch 16.

The above-described elements are employed in a manner well known in the art. Thus, with the slide retracted, a workpiece 30 is placed on the die plug 20 and the press is actuated to cause the slide 10 to move through its down stroke. The punch 16 engages workpiece 30 and causes the piece to be formed to the configuration shown in FIG. 1. Thereafter, the slide is retracted with the workpiece 30 frictionally retained within the punch 16. At this point, it is necessary that the workpiece be ejected from the punch preparatory to the next working cycle and it is for this purpose that knock-out mechanisms are employed.

To accomplish this ejection function, there is provided a knock-out bar 32 which extends through slots 33 in the slide 10. The knock-out bar includes roll pins 34 which are adapted to engage a portion of the slide and retain the knock-out bar in a properly oriented position in the slide. The slot in the slide is larger than the knockout bar so that relative movement between the slide and bar is permitted. The frame 12 is slotted at 3-6 so that either end of the knock-out bar 32 is received within the slots.

A knock-out pin 38 is associated with each end of the knock-out bar. As shown best in FIG. 3, each end of the knock-out bar comprises a split clamp in which the knock-out pin is received with a threaded fastener 40 provided to compress the split ends of the knock-out bar into frictional engagement with the pins 38. As is apparent, the position of the pins 38 may be adjusted relative to bar 32 simply by releasing fasteners 40, moving the pins to the desired position and re-tightening the fasteners.

At least one die pressure pin 42 extends through the punch holder and the face of the slide into engagement with the knockout bar 32. The other end of the pressure pin rests against the knock-out plate 26.

The above described knock-out mechanism operates in the following manner. As the slide travels through its down stroke or work cycle, the die pressure pin 42 forces the knock-out bar 32 in an upward direction away from the face of the slide. This occurs due to the action of the knock-out plate 26 engaging the surface of the workpiece 30 and thereby being forced upward into engagement with the punch holder 14. As the knock-out plate moves upward, so also the die pressure pins 42 are forced upward and the assembly of parts assume the relationship shown in FIG. 1. It should be noted that in this position of the parts, the knock-out pins 38 and the knockout bar 32 are positioned in the lower region of the slots 36 in the frame 12.

During the upstroke or retract cycle of the press, the punch 16, knock-out plate 26, pressure pins 42 and knockout bar 32 retain the position illustrated in FIG. 1 until the retraction of the slide causes the upper end of the knock-out pin 38 to engage the inner end or surface 44 in the slots 36. At this point, further travel of the knockout bar 32 is prevented. As the slide continues its upward movement, the knock-out bar 32, the pressure pin 42 and the knock-out plate 26 remain stationary so that there is relative movement between the punch 16, carried by the slide, and the knock-out plate 26. This relative movement causes the knock-out plate to eject the workpiece from within the punch 16 in a manner shown in FIG. 2.

It will be appreciated that as the operation of the press is reversed, the parts and elements will return to their original position.

It is thus apparent that the above-described mechanism, although extremely simple in construction, functions in an entirely satisfactory manner to eject the workpiece from the die. Contrasted with the prior art, the described arrangement requires no brackets or adjusting mechanism on the frame of the press, thereby eliminating both the expense of manufacturing the brackets or adjusting mechanism as 'well as the expense of machining the press frame to accommodate such brackets and adjusting mechanism. All that is required is that the frame have a simple abutment surface, such as surface 44, against which the ends of the knock-out pins 38 may abut. The fasteners 40 permit adjustment of the pins 38 so that ejection occurs at the proper point in the stroke cycle.

An additional feature of the adjustable connection between the knock-out pins 38 and the knock-out bar 32 should be noted. The fasteners 40 which clamp the knockout pins in the knock-out bar normally are sufficiently tightened that the pins will not slip relative to the knockout bar when the pins are in abutment with the surface 44; however, in the event of improper adjustment of the knock-out mechanism or in case an overload condition should occur, the clamp arrangement of the pins 38 does permit the pins to slip relative to the knock-out bar. Thus, there is a built in mechanism which minimizes the possibility of damage to the press and dies.

It is apparent that the above-described mechanism fully accomplishes the objects and advantages set forth hereinabove. Modification and alterations in the invention will suggest themselves to having ordinary skill in the art and it is intended that such modifications and alterations are to be included within the scope of the invention as defined by the appended claims.

Having thus described my invention, I claim:

1. In a press having a frame and a slide reciprocably mounted in said frame, said slide having a slot therethrough, a knock-out bar extending through said slot in said slide, said knock-out bar having opposite end portions, split clamp means on said opposite end portions, elongated knock-out pin means adjustably received in said clamp means and extending parallel to the path of travel of said slide, fastener means for tightening said clamp means into frictional gripping engagement with said pin means, pressure pin means carried by said slide below said knock-out bar, and abutment surfaces on said press frame above said knock-out pin means, said knockout bar being movable upwardly with said slide and said knock-out pin means being engageable with said abutment surfaces to limit upward movement of said knockoutbar.

2. The device of claim 1 wherein said frame has slots formed therein, said slots having inner end surfaces defining said abutment surfaces.

References Cited UNITED STATES PATENTS 324,812 8/1885 Clapp 72-345 1,917,743 7/1933 Walker 72 344 2,451,511 10/1948 Rice 72-345 RICHARD J. HERBST, Primary Examiner 

